Accumulation of Microplastics in the Brain: A Link to Dementia?

In March 2024, an Italian study reported the detection of plastic nanoparticles (1–1000 nanometres) and microparticles (1–1000 micrometres) in atherosclerotic plaques of the carotid artery in 58% of patients who had undergone carotid endarterectomy (see our article on this topic). The presence of plastic particles in a plaque was associated with a 4.5 times higher risk of death or major cardiovascular events, compared to patients whose plaques did not contain plastic. Although the results of this study do not establish a causal link between the presence of plastic in atherosclerotic plaques and cardiovascular disease, they are considered highly concerning by the scientific and medical communities.

Micro- and nanoplastics (MNPs) have been detected in almost every organ of the human body (see Figure 1). Until now, few studies have reported the presence of MNPs in the brain; however, a recent American study reports the presence of large quantities of MNPs in this organ. In this study, published in the journal Nature Medicine, researchers used cutting-edge technologies (gas chromatography coupled with mass spectrometry, infrared spectroscopy, and electron microscopy) to measure the quantity of MNPs in the brain, liver, and kidneys from autopsies of individuals who died between 2016 and 2024.

The results indicate the presence of 12 types of plastic polymers in all three organs, with polyethylene (PE) being the most abundant—particularly in the brain, where it accounts for 75% of the MNPs. MNP concentrations in the liver and kidneys were similar, with median values of 433 and 404 µg/g, respectively. Brain samples (from the frontal cortex) contained significantly higher quantities of MNPs than the liver and kidneys: 3,345 µg/g for samples obtained in 2016 and 4,917 µg/g for those obtained in 2024. Thus, MNPs accumulate in the brain 7 to 12 times more than in the liver and kidneys—an enormous difference that could have harmful consequences for brain function.

Researchers also obtained samples from individuals who had dementia at the time of death, as well as, for comparison, samples from people who died without dementia. Analysis of MNPs in brain samples revealed a median concentration of 26,076 µg/g of tissue in individuals with dementia—a much higher concentration than that found in normal brains, which was 4,917 µg/g. Microscopic examination of the tissue showed that the plastic particles were mostly nanoparticles (<1 µm) in the shape of rods, shards, or flakes.

The presence of MNPs in the three organs was not influenced by age, gender, race, or cause of death. However, MNP concentrations in liver and brain tissues collected during autopsies in 2024 were significantly higher than in samples from 2016. The researchers estimated that brains collected in 2024 contained approximately 50% more MNPs than those collected eight years earlier in 2016. This increase may be due to the exponential rise in environmental MNPs, but this remains to be confirmed.

One common criticism of such studies is the possibility of contamination from plastic containers during storage and handling. However, the researchers implemented extensive controls, and the hypothesis of significant contamination can be ruled out.

The presence of large amounts of MNPs in the brains of people with dementia is intriguing, but does not establish a causal link. It is possible that individuals with dementia had poor diets for many years before death (e.g. ultra-processed foods, fast food, soft drinks), which could have led to higher ingestion and thus accumulation of plastics. It is also plausible that the neurodegenerative pathology itself, associated with dysfunctions in the brain’s waste clearance systems, may have favoured the accumulation of MNPs—without being the direct cause of dementia.

Future studies using more refined protocols and advanced analytical techniques, and conducted in much larger cohorts, are needed to better understand the impact of plastics in the brain. Given the exponential increase in environmental plastics, the scientific community must strive to determine whether MNPs play a role in neurological disorders and other aspects of human health.